Viscous bypass coupling for torque converter

ABSTRACT

A bypass drive line (27) for a torque converter type automatic transmission (11) in which the bypass drive line includes a viscous coupling (30). The viscous coupling is of a sandwich construction including an annular body member (32) formed of aluminum, an annular cover member (34) of steel secured at its outer periphery (34a) to the outer peripheral portion (32a) of the body member and radially inwardly thereof spaced axially from the body member to define a viscous fluid chamber therebetween, and an annular clutch member (36a) disposed in the chamber and having a central hub portion (36e) adapted to be drivingly connected to the output shaft (16) of the torque converter. Confronting portions (36e, 32f) and (36c, 36d) of the body and clutch members define closely spaced working area, for viscously transmitting force from the body member to the clutch member. The drive into the coupling from the housing (22) of the torque converter is through an annular steel clutching surface ( 34f) defined on the side face of the radially outer peripheral portion of the cover member. The body member includes a central hub portion (32d) which is journaled on the central hub portion of the clutch member and the radially inner periphery (34d) of the cover member is sealed to the clutch member in non load-bearing relation so that the entire radial loading of the body member and cover member are carried at the journal between the hub portion of the body member and the clutch member. And a thrust arrangement (42) is provided on the extension of the coupling having thrust washers 44, 48 which react axial forces at a position radially outward of the journal inhibit cocking of the body hub on the clutch hub.

BACKGROUND OF THE INVENTION

This invention relates to viscous couplings. More particularly, itrelates to such couplings employed in automatic fluid coupling or torqueconverter transmissions to selectively bypass the torque converter.

Torque converter type automatic transmissions have achieved almostuniversal application and acceptance in motor vehicles. While generallysatisfactory in this application, torque converter automatictransmissions embody inherent slip and therefore incorporate inherentlosses in vehicular fuel economy. In an effort to minimize this slippageand thereby optimize fuel economy, various efforts have been made tobypass the torque converter with some manner of direct drive which istypically brought into play when the vehicle is operating in the highergear ratios and above a predetermined vehicular speed. While thesedirect drive bypass arrangements have resulted in improvements in fueleconomy, they have also, under certain conditions, served to transmitvarious drive line vibrations to the passenger compartment of the motorvehicle, resulting in a derogation in the ride quality of the vehicle.In an effort to provide a bypass arrangement that would not transmitdrive line vibrations to the passenger compartment, it has been proposedthat a viscous coupling be employed in the bypass drivetrain. While theuse of a viscous coupling in the bypass drivetrain does serve tominimize transmission of drive line vibrations to the passengercompartment, it is imperative that the coupling be designed for maximumefficiency so that losses in the coupling itself cannot significantlyoffset the fuel economy gains achieved by the use of the bypass.

Further, since viscous couplings transmit torque across closely spacedinternal surfaces via a viscous fluid, it is not only imperative thatthe spacing between the surfaces be uniform from one coupling to anotherbut that such spacing be maintained while the coupling is in use. Whenviscous couplings are employed in bypass drivetrains, they are or may besubjected to relatively high axial loads which tend to distort theirhousings, thereby changing the spacing between the surfaces.Additionally, nonuniform axial loads on the housings tend to cock thehousings and cause metal-to-metal contact of the internal surfaces,thereby causing dramatic derogation of the couplings performance andpremature failure.

Viscous couplings employed in automatic torque converter transmissionsto selectively bypass the torque converter must transmit relatively hightorques and therefoe must have large viscous sheer surfaces, must berelatively compact to fit within the housing of the torque converter,must be manufacturable at reasonable and competitive cost, must exhibituniform torque transmitting capacities from coupling-to-coupling, andmust be durable. Accordingly, the viscous coupling disclosed herein isformed with an annular housing having an annular radially extending bodymember formed preferably as an aluminum casting, an annular radiallyextending cover member formed as a ferrous sheet metal stamping, aclutch member formed as a permanent mold casting disposed in a chamberdefined by the housing. The body member includes an axially extendinghub portion having an inner peripheral surface and the clutch memberincludes an axially extending hub portion having an outer peripheralsurface on which the inner peripheral surface of the hub portion of thebody member is journaled. The hub provides the sole radial and axialload support for the housing. And an outer peripheral portion of thesteel cover member, fixed to an outer peripheral portion of the bodymember, defines an annular axially facing friction surface for clutchingcoaction with a confronting friction surface defined by the torqueconverter housing.

SUMMARY OF THE INVENTION

Accordingly, it is the object of the present invention to provide simpleand efficient viscous couplings for use as bypass elements in torqueconverter transmissions and which are compact, lightweight, inexpensive,and durable.

The torque converter viscous bypass coupling of the present invention isof the type including an annular body member, an annular cover membercoacting with the body member to define an annular chamber for receivinga viscous fluid, and an annular clutch member disposed within thechamber in viscous driving relation to the body member and having a hubportion adapted to be drivingly connected to the output shaft of thetorque converter.

According to one feature of the invention, the body member is formed ofaluminum and has a central hub portion which is journaled on the centralhub portion of the clutch member, the cover member is formed from alightweight ferrous sheet metal stamping and is sealed adjacent itsradially inner edge to the clutch member but is nonload-bearing so thatthe entire radial and thrust loading of the body member and cover memberis absorbed at the hub portions of the body and clutch members, and anouter peripheral surface of the steel cover member defines an annularaxially facing friction surface for clutching coaction with aconfronting friction surface defined by the torque converter housing.This arrangement provides a lightweight, inexpensive, and compactcoupling with good heat transfer, and negates the need for bonding afriction material to the body member to protect the aluminum of the bodymember from wear and abrasion.

According to another feature of the invention, outer peripheral portionsof the body and cover members are fixed together by metal rollover, andcircumferential slippage of the members is prevented by projections fromone member into recesses in the other member.

These and other objects, features, and advantages of the invention willbecome apparent from the following Detailed Description of the PreferredEmbodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a motor vehicle drivetrain including atorque converter type automatic transmission employing a torqueconverter bypass drive embodying a viscous coupling;

FIG. 2 is a fragmentary cross sectional view on an enlarged scale of thetorque converter and viscous coupling bypass seen schematically in FIG.1; and

FIG. 3 is a fragmentary end view looking along line 3--3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The motor vehicle drivetrain seen schematically in FIG. 1 includes aninternal combustion engine 10, an automatic transmission 11 and apropeller shaft 12 driving rear or front wheels 13 through adifferential 14.

Transmission 11 includes a torque converter 15 having an output shaft 16and a gear ratio box 18 driven by torque converter output shaft 16.Torque converter 15 is filled with automatic transmission fluid andincludes, in known manner, a pump 20 driven from engine 10 throughtorque converter housing 22, a stator 24, and a turbine 26 drivenhydrokinetically by pump 20. A fluid coupling may be employed in lieu ofa torque converter.

Torque converter 15 further includes a bypass drive line seen generallyat 27 in FIG. 1. Bypass drive line 27 is effective when actuated toprovide a direct drive between torque converter housing 22 and torqueconverter output shaft 16 through a viscous coupling 30 therebybypassing the high slippage drivepath through pump 20 and turbine 26.

Turbine 26, as seen in FIG. 2, is secured by welding at 28 to an annularsleeve or mounting member 29. The inner periphery of the sleeve issplined at 29a for coaction with splines 16a on output shaft 16 toeffect rotation of shaft 16 in response to rotation of turbine 26; aseal 31 prevents flow of transmission fluid along the interface of thesleeve and output shaft.

Viscous coupling 30 is generally circular and somewhat L-shaped inradial cross section. The coupling is of a sandwich construction andincludes an annular housing assembly, adapted to be positioned withintorque converter housing 22 of the torque converter and has axiallyspaced annular side wall members defining an annular clutch chambertherebetween, and an annular clutch member disposed within the clutchchamber. One side wall of the annular housing is constituted by a bodymember 32 and the other side wall member of the annular housing isconstituted by a cover member 34. A clutch member 36 is interposedbetween body member 32 and cover member 34. Cover 34 is formed as asteel stamping and body member 32 and clutch member 36 are formed asaluminum castings.

Body 32 includes a radially outer peripheral portion 32a, anintermediate or working portion 32b, and a radially inner portion 32cterminating in a hub portion 32d extending axially leftwardly as viewedin FIG. 2 from the radially inner edge of inner portion 32c.Intermediate or working portion 32b is machined on its inner or leftface, as viewed in FIG. 2, to form a series of annular axially extendingrings 32e radially separated by a series of annular grooves 32f. A seal33 is disposed in another annular groove machined in the inner face ofbody 32 radially outwardly of lands and grooves 32e, 32f.

Cover 34 includes a radially outer peripheral portion 34a held in aposition seated against the inner or left face of body outer peripheralportion 32a by a rollover 32g on body 32, a plurality of tangs 34breceived in blind bores or recesses 35 to prevent slippage of the coverrelative to the body member, an intermediate portion 34c, and a radiallyinner portion 34d terminating in an inwardly, or rightwardly, turned lipportion 34e.

Intermediate portions 32b and 34c of the body and cover are configuredto define the chamber which receives clutch assembly 36.

Clutch assembly 36 includes a working portion 36a and a mounting portion36b. The side of working portion 36a confronting body 32 (the right sidein FIG. 2) is machined to form a series of annular axially extendingrings 36c separated by a series of annular grooves 36d. Rings 32e onbody 32 are interdigitally arranged with respect to rings 36c on clutch36. Mounting portion 36b includes an annular radially extending mountingflange or bridge portion having a plurality of openings to allowcirculation of the viscous fluid in the chamber, and an annular axiallyextending hub portion 36e extending rightwardly and leftwardly of flangeor bridge. The inner periphery of clutch hub portion 36e includessplines 36f which co-act with splines 29b on the outer periphery ofsleeve 29 to effect rotation of clutch assembly 36 with output shaft 16and allow limited sliding movement of hub 36e to effect axial movementof the coupling. A seal 38 prevents flow of transmission fluid along theinterface of the sleeve and hub portions. Annular wear sleeves 40 and 41of hardened steel are pressed onto the rightward and leftward outerperipheries of clutch hub portion 36e. The inner periphery of body hubportion 32g is journaled on the outer periphery of clutch hub portion36e defined by sleeve 40. Sleeve 40 and clutch hub portion 36e includeopenings 40a and 36i defining a drain opening leading to passagesdefined by splines 36f and 29b for preventing buildup of high-pressuretransmission fluid from the right side of the coupling.

Hub portion 32d is axially positioned with respect to clutch assembly 36and inhibited against cocking due to nonuniform axial forces on bodymember 32 by thrust means 42 which react axial forces on body member 32in both directions. The thrust means include an annular radiallyextending washer 44 formed from steel and axially secured against therightward end of wear sleeve 40 by a snap ring 46 retained in an annulargroove in clutch hub portion 36e and an S-shaped thrust washer 48.Thrust washer 48 is secured at its radially outer periphery against aradially extending surface 32i by a rollover 32h and extends radiallyinward to a position overlapping and sandwiching thrust washer 44between its inner face and surface 32i with a relatively small runningclearance therebetween.

Sleeve 40 and thrust means 42 function to absorb the entire bearing loadof body member 32 and cover member 34, i.e., radial loads, uniform axialloads and nonuniform axial loads which tend to cock hub portion 32d onclutch hub portion 36e and reduce the critical spacing between workingportions 32b and 36a on one diametrical side of the coupling andincrease the critical spacing on the other diametrical side. Thisspacing is critical from a design standpoint since it determines theamount of viscous driving force or torque transmitted from body member32 to clutch assembly 36. The described thrust means reduces the numberof dimensions needed to set the spacing during assembly of the couplingand reduces the effect of nonuniform axial forces on the body member.

Nonuniform axial forces, which tend to cock body hub portion 32d onclutch hub portion 36e, are reacted at a position radially outward ofthe journal or radial bearing surfaces defined by the inner and outerperipheral bearing interface between the hubs. For example, should theconnection of the outer peripheral portion 32a of the body member not benormal to the bearing interface between the hubs, one diametrical sideof the body member will be pushed to the left and the other diametricalside will be pulled to the right. Any cocking of this nature accelerateswear of the journal or radial bearing surfaces and if severe enoughcauses axial and radial metal-to-metal contact of the rings in workingportions 32b and 36a. Since the interface of thrust washers 44, 48 isdisposed radially outward of the radial bearing surface, they in effectchange or reduce the mechanical advantage of the nonuniform forces,thereby reducing the cocking forces on the radial bearing interfacewhile holding the critical spacing between the working means. That is,should hub portion 32d tend to cock relative to hub portion 36e, theradially outer portion of washer 44 will contact portions of eithersurface 32i or washer 48 at a position radially outward of the journaland the seals.

With respect to reducing the number of dimensions needed to set theaxial spacing between working portions 32b and 36a of the body memberand the clutch assembly, the length of sleeve 40 and the runningclearance between thrust washers 44, 48 set the minimum and maximumaxial spacing. Further, since the running clearance is exterior of thecoupling, this dimension is readily checked during assembly of thecoupling and is lubricated at all times by the surrounding oil in thetorque converter housing.

The radially outer peripheral portion 34a of cover member 34 defines aradially extending friction surface 34f which co-acts with a loosefriction material or lining 58 sandwiched between a friction surface 22adefined by the torque converter housing 22. In copending patentapplication Ser. No. 388,557 the outer periphery of the steel covermember is disposed radially inward of an annular friction lining whichis adhesively bonded to the aluminum body member. By extending steelcover 34 radially outward to define a clutching or friction surface, thebonding operation becomes unnecesary.

The radially outer peripheral portion 34a of cover member 34 may beextended and formed with a cylindrical wall portion that embraces theouter peripheral surface of the body member. The cylindrical wall maythen be rolled down over the body member. Further, tangs 34b may bereplaced by dimpling or rolling the cylindrical wall of the cover memberinto notches or recesses formed in the body member.

The viscous coupling is filled with a silicone fluid, for example,dimethyl polysiloxane. The silicone liquid is prevented from escapingradially outwardly by the previously mentioned elastomeric square cutsealing ring seal 33. The silicone fluid is prevented from escapingradially inwardly by a pair of double lip elastomer seals 54, 56. Seal54 is positioned in an annular recess 32j in clutch hub portion 32d andruns against steel sleeve 40. Seal 56 is positioned in lip portion 34eand runs against steel sleeve 41. The seals also preclude leakage ofautomatic transmission fluid into the viscous coupling. If desired,sleeve 40 may be made in two shortened pieces, one pressed on hubportion 36e for sealing coaction with seal 54 and the other pressed intothe bore defined by the inner periphery of hub portion 32d.

In the operation of the bypass drive line 27, automatic transmissionfluid is normally admitted to the torque converter environment throughthe annular passage or chamber 60 formed between cover 34 and torqueconverter housing 22. The presence of the fluid in chamber 60 actingagainst cover 34 moves the viscous coupling to the right against arelatively light force provided by a spring 62 as viewed in FIG. 2 toits disengaged position (see in FIG. 1) wherein lining 58 is separatedfrom housing surface 22a and surface 34f of the cover member to form anannular passage past the lining. The fluid thus flows radially outwardlyin passage or chamber 60, past lining 58, and into the main chamber ofthe torque converter. When it is desired to engage the bypass driveline, as, for example, when the vehicle is operating in a higher gearratio and above a predetermined vehicle speed, the direction of flow ofthe automatic transmission fluid in the torque converter is reversed byactuation of a suitable solenoid valve, not shown. Specifically, theautomatic transmission fluid is now admitted to the main chamber of thetorque converter where it acts against body 32 and slides the viscouscoupling to the left as viewed in FIG. 2, to bring lining 58 intofrictional engagement with housing and cover member surfaces 22a and34f. The transmission now drives directly through the viscous couplingto output shaft 16, thereby bypassing the torque converter. Althoughthere is a limited amount of slip in the viscous coupling occurringbetween body 32 and clutch 36, this slippage is significantly less thanthe slippage in the torque converter so that the overall efficiency ofthe transmission is significantly increased with correspondingimprovements in vehicular fuel economy. And the viscous coupling,because of its cushioning effect, has the effect of eliminating thedrive line vibrations that are transmitted to the passenger compartmentin prior art bypass drive lines employing a solid mechanical drivingconnection. Overheating of the transmission fluid, when the viscouscoupling is frictionally engaged with the torque converter housing, isprevented by allowing cooling oil to flow through an axially extendedopening 64 disposed radially inward of lining 58.

In some automatic torque converter transmissions, clutch assembly 36 mayconnect to a shaft which bypasses the torque converter wherever thetransmission is shifted into some predetermined ratio or ratios.Accordingly, the friction clutch may be dispensed with and the outerperipheral portion of the viscous coupling may then be mechanicallyconnected to the torque converter housing.

The disclosed viscous coupling design provides simple, efficienttransmission of power through the viscous coupling. Further, couplingsof this design are readily formed and assembled with relatively lowmass-production costs while still providing uniform torque transmittingcapacities and long life in use even when subjected to nonuniform axialforces when they are frictionally or mechanically connected to torqueconverter housings.

While a preferred embodiment of the invention has been illustrated anddescribed in detail, it will be apparent that various changes andmodifications may be made in the disclosed embodiment without departingfrom the scope or spirit of the invention.

What is claimed is:
 1. In a viscous coupling of the type including anannular housing assembly adapted to be positioned within the housing ofa fluid coupling and defining an annular chamber containing a viscousfluid, the fluid coupling housing having an annular friction surfaceadapted for clutching coaction with the annular housing; an annularclutch assembly disposed in the chamber including an axially extendinghub portion adapted for rotational driving and sliding connection to ashaft in the fluid coupling housing and an annular radially extendingclutch portion having working means for viscous clutching coaction witha corresponding working means on a confronting portion of the annularhousing; seal means cooperating between the annular housing and theclutch hub portion; the improvement comprising:first and second radiallyextending annular side wall members forming said annular housing anddefining said chamber, said first side wall member formed of aluminumand having an annular axially extending hub portion at its radiallyinner edge journaled on the outer peripheral surface of the clutch hubportion, said side wall hub portion and said clutch assembly providingthe sole radial and axial support for the housing assembly, and saidsecond side wall member being formed of a ferrous metal having anannular radially extending portion at its outer periphery fixed to anouter peripheral portion of the first side wall member and defining anannular clutching surface for said clutching coaction with said annularfriction surface of said fluid coupling housing.
 2. The viscous couplingof claim 1, wherein said outer pheripheral portions of said first andsecond side wall members are fixed together by a metal rollover, andcircumferential slippage of said members is prevented by a projectionfrom one of said members into a recesse in the other member.
 3. Theviscous coupling of claim 2, wherein said projections and recessescomprise:blind openings in the outer peripheral portion of said firstside wall member; and tangs defined by said second side wall member andreceived in said blind openings.
 4. The viscous coupling of claim 1,wherein said journal is axially spaced from the annular radiallyextending clutch portion and said said seal means includes a sealdisposed therebetween.
 5. The viscous coupling of claim 4, wherein saidclutch hub portion includes a drain opening extending radially inwardfrom an edge of said journal to a passage extending axially in thedirection of the second side wall member.
 6. The viscous coupling ofclaim 1, further including:thrust means reacting axial forces on saidfirst side wall member for inhibiting changes in the axially spaceddistance between said working means.
 7. The viscous coupling of claim 6,wherein said thrust means includes:a first thrust member extendingradially outward from the inner edge of and contacting a radiallyextending surface of said clutch hub portion of said first side wallmember for preventing axial movement of said hub portions relative toeach other; and a second thrust member having a radially outer edgefixed to said first side wall member at a position radially outward ofthe radially outer edge of said first thrust member and extendingradially inward to a position overlapping and sandwiching said firstthrust member between said radially extending surface of said one sidewall member and said second thrust member.
 8. The viscous coupling ofclaim 6, wherein said seal means includes first and second seals axiallydisposed on opposite sides of said clutch portion, said first sealdisposed between a radially inner surface of said first side wall memberand the outer peripheral surface of the clutch hub portion, and saidsecond seal disposed between said lip portion of said second side wallmember and the outer peripheral surface of said clutch hub portion; saidclutch hub portion includes with respect to said chamber an axiallyoutwardly facing end surface, an annular inwardly facing recesssupporting said first seal and said journal disposed therebetween; andwherein said thrust means includes:a first thrust member extendingradially outward from the inner edge contacting said end surface, andaxially fixed with respect to said clutch hub portion; and a secondthrust member having a radially outer edge fixed to said end surface ata position radially outward of the radially outer edge of said firstthrust member and extending radially inward to a position overlappingand sandwiching said first thrust member between said end surface andsaid second thrust member.
 9. The viscous coupling of claim 6, whereinsaid hub portions are principally formed of aluminum, said outerperipheral surface of said clutch hub portion is defined by a ferrousmetal sleeve pressed on said clutch hub portion for providing bearingsurface for the hub portion of said one side wall member and forproviding a wear surface of said first seal.
 10. The viscous coupling ofclaim 6, wherein said thrust means includes portions disposed radiallyoutward of said seal means for inhibiting said cocking.